Although the present invention is related to pipe replacement in general, for purposes of simplicity, the invention is discussed herein particularly as it applies to replacement of conventional sewer pipe which is employed in typical municipal environments. Typically, sewer pipe is composed of interconnected joints of pipe composed of concrete, clay tile or metal, including cast iron, steel or ductile iron. Sections of utility pipe are typically provided with enlarged bells at one end and a straight joining portion at the opposite end. Sections of utility pipe are placed in end-to-end relation with the straight portions thereof entering the enlarged bell of the adjacent pipe section. In the past, it has been considered unnecessary to establish absolutely sealed joints when utility pipes are laid. Thus, a small amount of leakage is typical. Moreover, utility pipes such as sewer pipes are seldom maintained under any pressure and therefore leakage is restricted only to a small amount of seepage at the pipe connections.
It has been found that utility pipes become deteriorated after having been buried for several years. It is now known that sewer gases cause deterioration of concrete material and also have an adverse effect on clay tile material and metal pipes. Upon deterioration of the pipe materials, the pipes can become fractured due to shifting or settling of the earth and in some cases the joints are pulled apart thereby allowing substantial leakage to occur at the pipe joints. It is desirable therefore to provide means for accomplishing replacement of utility pipes and to thereby restore the utility piping system to substantially new condition.
In many cases, the utility piping system of a municipality may have been initially established with relatively small diameter utility pipes. Additional fluid flow capacity may now be desired, such as to accommodate increased water usage or to provide for conversion of residential municipal areas to a large capacity commercial environment such as when large building structures or other commercialization is developed. To provide the additional flow capacity needed for commercial sewer systems, it is frequently necessary to replace the entire piping system with larger pipe or to install pipes in parallel relation to existing sewer systems. In such case, excavation is usually required. Sections of utility pipe are often located under roadways, sidewalks and other surface structures. Typical utility pipe replacement requires trenching to expose the pipe to be replaced which consequently requires replacement or renovation of sections of roadway, sidewalks, etc. It is desirable therefore to provide a system for replacement of utility pipes wherein surface utilities remain relatively undisturbed. In circumstances where higher volume liquid flow is required, it is desirable to provide for sewer line rehabilitation where the replacement pipe may have an internal diameter exceeding that of the pipe being replaced.
Another disadvantage of conventional municipal utility systems is that the various pipe sections there employed interfere with efficient flow of liquid. Each of the joints of the utility pipe in many cases constitute voids for deposit of sediment and create turbulence that inteferes with efficient fluid flow. It is therefore desirable to provide a system for utility pipe replacement wherein the inside surface of the replacement pipe will be substantially free from surface discontinuities such as typically occur in jointed utility pipe.
It has also been determined that leakage of sewage including liquid and gaseous materials into the surface earth formation can constitute severe health hazards such as pollution of surface water and shallow underground water. Leaked sewer gases can penetrate through the surface soil and collect in the residences and building structure to such extent that a health hazard becomes present. It is also desirable to provide a utility replacement system wherein leak free replacement pipe is installed.